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11/10/2016, 17:00

Mice sing like a jet engine to find a mate: Ultrasonic love songs could be the key to treating autism and stutters

Mice and rats sing ultrasonic songs to attract a mate and defend their territory.

Just how they produce the noise, which is inaudible to humans, has remained a mystery - until now.

In a new study, researchers have discovered the unique way in which the diminutive rodents sing.

Mice point a small air jet coming from the windpipe into their voice box to make the high-pitched whistle, likening the noise to that made by a jet engine.

Mice point a small air jet coming from the windpipe into their voice box to make the high-pitched whistle, likening the noise to that made by a jet engine

It has long been known mice use ultrasonic vocalisations to communicate.

Last year, experts from Duke University said male rodents have 'surprisingly complex' love songs, following specific patterns like a songbird's tune, instead of being random.

The mice also appeared able to modify their songs, making them louder and more complex when they could smell a female but not see her.

Longer and simpler songs were chosen when a male was wooing a female in his presence.

Neurobiologist Dr Erich Jarvis said: 'It is clear that the mouse's ability to vocalise is a lot more limited than a songbird's or human's, and yet it's remarkable that we can find these differences in song complexity.'

The discovery is of particular interest as the love songs of mice are studied to find cures for stuttering and autism.

‘We found that mice make ultrasound in a way never found before in any animal,’ said Elena Mahrt, lead author on the study and graduate student at Washington State University Vancouver.

Coen Elemans, senior author on the study and head of the Sound Communication and Behavior group at the University of Southern Denmark, explained: ‘Mice don't use vibrating vocal folds in their larynx [voice box] to make these ultrasonic sounds.

‘Instead they point a small air jet coming from the windpipe against the inner wall of the larynx.’

‘This produces an ultrasonic whistle.’

To make the discovery, the researchers recorded the action using an ultra-high-speed video capable of producing 100,000 frames per second.

They were able to show the vocal folds remain completely still while ultrasound was coming out of the larynx.

Co-author Anurag Agarwal, co-author and head of the Aero-acoustics laboratories at the University of Cambridge, said: ‘Interestingly this mechanism is known only to produce sound in supersonic flow applications, such as vertical take-off and landing with jet engines, or high-speed subsonic flows, such as jets for rapid cooling of electrical components and turbines

‘Mice seem to be doing something very complicated and clever to make ultrasound.’

Dr Elemens said many rodents use ultrasound to communicate and bats may even use it to echolocate.

‘Even though mice have been studied so intensely they still have some cool tricks up their sleeves,’ he added.

Dr Mahrt continued: ‘The more we understand how mice make their social sounds, the easier it will be to understand what happens in a mouse brain that has the same genetic mutation as a human with a speech or social disorder.’ 

The different regions of a mouse larynx are shown left, with the right image showing a clear increase of peak frequency of noise as the mouse sings

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